In this question, I already had an answer, but decided to edit it and add some clarification.
While I was editing, the "1 new answer has been posted" message appeared on top of the page, but I just continued editing.
When I was finished, I saw that my original answer was still there, and now I had two answers, one being the first (unedited) one, the other one my edited version.
There is no sign of me editing the answer though.
I use Chrome 14, and while editing I always stayed in the same page, i.e. didn't close the tab or refreshed before.